Generally, a writing instrument includes a cartridge, a spring, a barrel, and a cartridge control unit. Further, a clip is provided at a predetermined position on the writing instrument so that a user may put the writing instrument in his/her pocket and easily carry the writing instrument.
When the user desires to use the writing instrument, the cartridge control unit is manipulated to extend the cartridge out of the barrel. On the other hand, when the writing instrument is not in use, the cartridge control unit is manipulated to retract the cartridge into the barrel and thereby store the writing instrument in his/her pocket. The writing instrument including the cartridge control unit is manipulated to extend or retract the cartridge out of or into the barrel, using a button, a push part, etc.
A knock and a gear have been widely used as the cartridge control unit. A knock-type writing instrument is constructed so that the knock and the gear are provided along a central axis in the barrel. Such a construction requires additional space for installing the knock and the gear in the barrel, thus increasing the length and width of the barrel.
However, in order to use the conventional writing instrument, the cartridge must be extended using the cartridge control unit that is separately provided. After using the writing instrument, the cartridge must be retracted using the cartridge control unit, thus causing inconvenience to a user.
The conventional writing instrument is problematic in that a user's clothing may be stained by ink dispensed from the cartridge when the writing instrument is put, with the cartridge extended, in his/her pocket.
In the writing instrument including a cap as well as the cartridge control unit, the cap must be open to use the writing instrument, and closed after using the writing instrument.
The writing instrument with the cap is problematic in that the cap must be removed and replaced whenever a user uses the writing instrument, so that the cap is likely to be lost.
Further, the conventional cartridge control unit is disadvantageous in that loud tapping sound may be generated about four times due to the shape of the gear and the elastic force of the spring, when protrusions provided on an inner circumferential surface of the barrel come into contact with the gear rotating about the central axis of the barrel. Thus, a product of high quality is not offered to consumers.